Process for oil recovery using surfactant gels

ABSTRACT

A composition and process for recovering oil by injecting an aqueous solution into a subterranean oil-bearing formation through one or more injection wells, displacing the solution into the formation, and recovering the oil from one or more production wells. This aqueous solution contains one or more amphoteric alkyl amido betaine surfactants that form a viscoelastic surfactant gels that can reduce the interfacial tension (IFT) and increase the viscosity of the injection fluid simultaneously in certain oils and brines. These viscoelastic gels are tolerant to electrolytes and multivalent cations. They are shear reversible and adsorbed little on the reservoir rock. The viscosity of the gels is reduced when they encountered certain hydrocarbons but remains high when contacting water or brine. This allows the fluid to preferentially penetrate the oil-bearing portions of the formation and resulting additional oil recovery. These amphoteric viscoelastic surfactant gels are particular suitable for use with reservoirs and brines characterized by medium to high temperatures, higher salinity, higher concentrations of divalent cations, and low formation porosities.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on provisional application Ser. No.60/557,346, filed on Mar. 29, 2004 and is a Divisional application ofpreviously filed 11/081,232 filed Mar. 16, 2005.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

DESCRIPTION OF ATTACHED APPENDIX

Not Applicable

1. Field of the Invention

This invention relates to the field of Enhanced Oil Recovery (EOR). Morespecifically, it relates to a composition and process containingviscoelastic surfactant gels that have both surfactant and gellingproperties that simultaneously provides low water/oil interfacialtension (IFT) and increases the viscosity of the injection fluid usedfor residual oil recovery.

2. Background of the Invention

Crude oil is generally recovered from an oil-bearing reservoir by threeprocesses, designated primary, secondary and tertiary recovery. Thelatter is also known as Enhanced Oil Recovery. In primary recovery theoil is produced through a producer well by taking advantage of thepressure exerted on underground pools of oil by gas or water presentwith the oil. Approximately 20% of the original oil in place (OOIP) isrecovered by this process. Once the pressure has been exhausted, othermeans of recovering the remaining oil must be employed. In secondaryrecovery the well may be re-pressurized with gas or water injectedthrough one or more injection wells to recover approximately anadditional 20% of the OOIP. Other secondary recovery methods includeacidizing, fracturing, water flood, etc. After secondary recovery meanshave been exhausted, EOR processes can be employed to recover additionaloil up to approximately 60% OOIP.

Many EOR techniques have been disclosed in the past yet the EOR processis not widely used by the industry for several reasons. For example, inthe EOR processes employing chemicals, petroleum sulfonates andsynthetic alkylaryl sulfonates are predominantly used as the surfactantto lower the interfacial tension (IFT) between the residual oil and theinjection fluid in order to overcome the capillary forces trapping theoil. Partially hydrolyzed polyacrylamides are generally employed as theviscosifier for mobility control. Both the polymers and surfactants usedare not salt and multivalent cation tolerant and therefore either afresh water source or pre-treatment of the injection water is required.Also, a costly hydration unit is often required for the polymer in orderto properly dissolve and develop its viscosity. Furthermore, often ahigh concentration of the surfactant is required for proper oildisplacement, or, alkali is used with the surfactant to enhance theinterfacial tension and reduce the surfactant adsorption. In addition,the polyacrylamide may precipitate and cause serious formation damagewhen contacting the connate water containing multivalent cations. Mostpolymers are not stable at temperatures above 140° C. and areirreversibly degraded by shear. The huge up-front investment and productlimitations currently discourage the wide use of the EOR process. Thisis especially the case for many marginal fields, owned by smallerindependent companies even though the fields contain considerableresidual oil reserves.

The present invention relates to the composition and process forinjecting amphoteric viscoelastic surfactant gels into a subterraneanoil bearing formation through one or more injection wells, displacingthe fluid into the formation and recovering oil from one or moreproduction wells. The viscoelastic surfactant gels contain amphotericsurfactants, commonly known as betaines. These are used alone or incombination with certain other surfactants and/or polymers in an aqueousinjection fluid, to reduce the interfacial tension (IFT) between brinesand crude oils and increase the viscosity of the injection brine.

There are many citations in the prior art that have recognized the useof various amphoteric surfactants for water flood and other oil recoveryprocesses. U.S. Pat. No. 3,939,911 describes a three-surfactant systemcontaining a water soluble salt of an alkyl or alkylaryl sulfonate, aphosphate ester surfactant and sulfonated betaine for oil recovery informations having high temperature and high concentrations of polyvalentions. U.S. Pat. No. 4,130,491 describes the use of naphthenic acid basedbetaines for recovering mineral oil from oil deposits.

U.S. Pat. No. 4,193,452 employs a surface active amphoteric quaternaryammonium sulfonate and an aliphatic alcohol containing 5 to 8 carbonatoms to produce a thicken injection fluid for waterflooding. U.S. Pat.No. 4,216,097 uses amphoteric surfactants having an inner quaternaryammonium group linked to a terminal sulfonated or carboxylate group toreduce the oil-water interfacial tension in relatively high salinityaqueous media that include the presence of from subterranean reservoirsby injecting through one or more injection wells and producing the oilfrom one or more production wells, as is the intent of the presentinvention.

The recent US Patent Application 2004/0214725 employs quaternaryammonium salts and alkyl amido amine salts of inorganic acids and/ororganic acids to produce viscoelastic aqueous systems. These fluids aresuggested for use in fracturing, gravel packing, drilling, completionfluids, as well as several non-oilfield based applications.

None of these examples of the prior art disclose the use of amphotericsurfactants, preferably alkyl amido betaines, specifically chosen anddesigned to be used in aqueous injection fluids and especially inproduced brine without any water treatment or water softening to provideboth low IFT and mobility control for the recovery of residual oil byinjection into one or more injection wells, displacing the fluid intothe formation, and recovering the oil from one or more production wells.

OBJECT OF THE INVENTION

The present invention includes a composition for recovering crude oilusing amphoteric surfactants, specifically alkyl amido betaines,designed to be used alone or in combination with certain othersurfactants and/or polymers in an aqueous injection fluid, tosimultaneously reduce the IFT between water/oil and to increase theviscosity of the injection brine, and a process for recovering oil by(a) injecting an effective amount of said composition into asubterranean hydrocarbon containing formation through one or moreinjection wells and (b) significant quantities of divalent metal ions.The amphoteric betaines used in this case are based on tertiary aminesthey do not increase the viscosity of the injected fluid as do the alkylamido betaines of the present invention. They are primarily used tolower the IFT between the injection fluid and the residual oil. Asexplained in the example included in U.S. Pat. No. 4,216,097, xanthangum was used as a mobility control agent.

U.S. Pat. No. 4,554,974 discloses a method for recovering petroleum froma subterranean reservoir by injecting an aqueous slug of a mixture ofamphoteric surfactant to reduce the interfacial tension and a highmolecular weight polysaccharide gum as the thickener.

U.S. Pat. No. 4,825,950 uses a betaine as an IFT lowering surfactantalong with two different polymers to form an electrolyte tolerantinjection fluid for oil recovery. The first polymer is primarily forthickening and the second is used to prevent the first polymer and thesurfactant from interfering with each other through interaction and/orprecipitation.

U.S. Pat. No. 6,831,108 and recent US Patent Applications 2004/0082484and 2004/0176478 use zwitterionic/amphoteric surfactants such asdihydroxyl alkyl glycinate, alkyl amido ampho acetate or propionate,alkyl betaine, alkyl amidopropyl betaine and alkyl imino mono anddi-proprionates derived from certain waxes, fats and oils inviscoelastic surfactant based aqueous fluids systems useful asthickening agents in conjunction with an inorganic water-soluble salt ororganic additives such as phthalic acid, salicylic acid or their saltsfor suspending particles during the excavation of geologic formations.Also the intent of the viscoelastic fluids of the above citations is notto recover residual oil displacing the fluid into the formation, andrecovering the oil from one or more production wells.

The present invention requires minimum up-front investment and equipmentfor injection. In most cases, the produced water can be used as theinjection water without any costly water treatment, softening and sludgedisposal. It also minimizes any potential damage to the formation thatmay be caused by the incompatibility of the injected chemicals with theformation.

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides a new and improved EOR composition andprocess of recovering crude oil using one or more amphoteric surfactantsthat are characterized by the following structure:

Where,

R is C12 to C30 alkane or alkylene, R₁ and R₂ are the same or differentand preferably represent a low molecular weight alkyl residue,especially straight-chain alkyl residue with 1 to 4 carbon atoms, orhydroxy alkane; and n is 2 to 6.

This amphoteric surfactant(s) is chosen and designed to be used alone tosimultaneously reduce the IFT between water and oil and to increase theviscosity of the injection brine, or it can be used in combination withcertain other surfactants and/or polymers in an aqueous injection fluidcomposition to recover oil by (a) injecting an effective amount of saidcomposition into a subterranean oil containing formation through one ormore injection wells, and (b) displacing the fluid into the formation,and recovering the oil through one or more production wells.

DESCRIPTION OF FIGURES

FIG. 1 shows the oil recovered using a composition containing 0.5% byweight of a soya amidopropyl dimethyl betainelarylalkyl sulfonate blend(B0503-2).

FIG. 2 shows the viscosity versus shear rates using a canola amidopropyldimethyl betaine (B0503-3) in seawater.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a new and improved EOR composition andprocess of recovering crude oil using one or more amphoteric surfactantsthat are characterized by the following structure:

Where,

R is C12 to C30 alkane or alkylene, R₁ and R₂ are the same or differentand preferably represent a low molecular weight alkyl residue,especially straight-chain alkyl residue with 1 to 4 carbon atoms, orhydroxy alkane; and n is 2 to 6.

This amphoteric surfactant(s) is chosen and designed to be used alone tosimultaneously reduce the IFT between water/oil and to increase theviscosity of the injection brine, or it can be used in combination withcertain other surfactants and/or polymers in an aqueous injection fluidcomposition to recover oil by (a) injecting an effective amount of saidcomposition into a subterranean oil-bearing formation through one ormore injection wells, and (b) displacing the fluid into the formation,and recovering the oil through one or more production wells. Theamphoteric surfactant is used in amounts form about 0.15 to about 10% byweight, the amount chosen to give the desired IFT lowering and viscosityincrease deemed necessary to recover residual oil.

The alkyl amido betaines of the present invention are derived from anyof a number of fatty acids and glycerides. Fatty acids include, but arenot limited to, lauric, lauroleic, myristic, myristoleic, palmitic,palmitoleic, stearic, iso-stearic, oleic, linoleic, ricinoleic, licanic,elaeostearic, arachidic, behenic, docosenic, lignoceric, tetracosenoic,and other saturated, unsaturated and polyunsaturated acids in the C12 toC30 range. Glycerides that can be used, include but are not limited tothose found in, canola oil, castor oil, coconut oil, corn oil, cottonseed oil, herring oil, jojoba oil, lard oil, linseed oil, menhaden oil,mustard seed oil, oiticica oil, olive oil, palm oil, palm kernal oil,peanut oil, perrilla oil, rapeseed oil, sunflower seed oil, sperm oil,tall oil, tallow, tung oil, whale oil, and other oils containingmixtures of C12 to C30 fatty acids as their glycerides.

The alkyl amido betaines are produced by any of the commonly knownmethods of manufacturing betaines including, but not limited to, thereaction of an alkyl amidopropyl amine with sodium chloroacetate orchloroacetic acid. A thorough description of the structures, propertiesand methods of preparation of various betaines can be found in Chapter 3Betaines by Xavier Domingo in Amphoteric Surfactants 2^(nd) Edition,Surfactant Science Series, E. Lomax ed., Marcell Dekker (1996).

The use of the betaines derived from these fatty acids and glyceridesoffers many advantages. They are produced from renewable resources. Theyare easily and inexpensively manufactured. They are readilybiodegradable. They are generally non-toxic to marine, mammalian andplant life. In many case, they provide both the functions of loweringIFT and increasing viscosity in a wide range of salinities andmultivalent ion containing brines.

We have found that the amphoteric alkyl amido betaine surfactants havingthe structure above have both unique viscoelastic gel properties and IFTreduction properties in certain water/oil systems and that they areideally suited for Enhanced Oil Recovery applications. These betainesare distinguishable from other amphoterics because they can only existin the cationic form in strong acid and the nonionic form at higher pHvalues. Other amphoterics can exist in their cationic form at low pH, asnonionics at an intermediate pH and as anionic surfactants at higher pH.Also the alkyl amido betaines of this invention are preferred over otherbetaines such as alkyl dimethyl betaines because they can formviscoelastic solutions at relatively low concentrations and in mostcases can also lower the IFT of the viscoelastic surfactant gel solutionagainst hydrocarbons. However, in certain cases, alkyl dimethyl betainescan be combined in relatively low concentrations with alkyl amidobetaines to form systems that lower IFT and increase viscosity and thiscombination is within the scope of our invention. In some cases theamphoteric viscoelastic surfactant gels of the present invention chosenfor a typical application are the mixtures of one or more different alkyamido betaines in order to optimize their properties. This is especiallytrue where naturally occurring fats and oils are used as the startingmaterials to synthesize them. These naturally occurring fats and oil aremixtures of fatty acids and the amphoteric alkyl amido betaines derivedfrom them are likewise mixtures.

The present invention provides a composition having both the viscosityrequired for mobility control and low IFT required to overcome thecapillary forces trapping residual oil. The present invention istolerant to electrolytes and multivalent cations and stable at hightemperatures with minimal adsorption onto the formation. The presentinvention is particular suitable for conditions where the existingtechnology is technically or economically unfeasible, such as forformations having low permeabilities, processes employing injectionbrines and/or connate water of high salinity and high multivalent cationconcentrations and for reservoirs that have been channeled by previouswaterflooding.

The compositions of the present invention using viscoelastic surfactantgel containing alkyl amido betaines may lose their viscosity uponcontacting crude oil or other hydrocarbons. This characteristic resultsin preferential flow of the visco-elastic surfactant gel through thoseportions of the formation that contain significant residual oilsaturation resulting in additional displacement of oil.

Because of the different properties of the formation, crude oil, connatebrine, injection brine, bottom hole temperature, etc., otherconstituents including other surfactants may be used with the amphotericalkyl amido betaine surfactant to further enhance its IFT and viscosityproperties. The secondary surfactants may be any of those generallyknown to those familiar with the art and include anionic, nonionic orcationic surfactants. The concentrations of these secondary surfactantsused are generally from about 0.01% to about 5% by weight.

Polymers may be used to provide residual viscosity control when theviscosity provided by the amphoteric alkyl amido betaine surfactant hasbeen reduced significantly upon contact with the oil in the reservoir.This residual viscosity is used to prevent the injection fluid fromover-riding the oil. The optional polymer maybe chosen from a number ofpolymers generally known to those familiar with the art including butnot limited to polyacrylamide, xanthan gum, guar gum, and cellulose.Polyacrylamide is the preferred polymer for this application and theconcentration used is from about 0.01% to about 0.5% by weight.

Also, we have found that it is very important to chose and design theproper alkyl amido betaine(s) for the oil/water system where it is to beemployed in order to optimize IFT lowering and viscosity buildingproperties under the applied field conditions.

The following examples further illustrate the object and the desirableproperties obtained with the present invention.

EXAMPLE 1

This example illustrates the use of an amphoteric alkyl amido betainesurfactant derived from naturally occurring vegetable oils, tosimultaneously lower the IFT of the brine/oil and increase the viscosityof the brine for an Asian oil field application.

The amphoteric surfactant, designated as B0503-1, was prepared byreacting 0.333 mole of soybean oil with 1.000 mole of dimethyl aminopropyl amine (DMAPA). The resulting soya amidopropyldimethyl amine wasfurther reacted with sodium chloroacetate in the presence of the properamount of a 1:1 by weight mixture of water and butyl cellosolve toproduce the soya amidopropyldimethyl betaine (sample no. B0503-1) withan active concentration of 50% by weight.

The brine from an Asian oil field, designated as Oil Field A, contained32,000 ppm total dissolved solids, 1,850 ppm of the multivalent cations,and the crude oil had an API Gravity of 22. The bottom hole temperaturewas 60° C.

The IFT was measured using a University of Texas Model 500 Spinning DropTensiometer after spinning for a period of 30 minutes. The viscosity ofthe brine-surfactant mixture was measured using a Brookfield LVTviscometer at 60° C. The results of these measurements are shown inTable 1. TABLE 1 IFT and Viscosity properties for Field A B05030-1,conc., % wt 0.30% 0.50% IFT, mN/m 0.0014 0.0038 Visc @ 12 RPM, cps 21 39Visc @ 30 RPM, cps 18 27

The data in Table 1 shows that the B0503-1 provides both low IFT andsufficient viscosity for Oil Field A. The samples were then aged for 30days in an oven set at 60° C. and no apparent changes in the IFT orviscosity were observed.

EXAMPLE 2

This example illustrates that B0503-1 from example 1 does not providelow IFT in Oil Field B—a west Texas Oil Field. This problem was resolvedby adding an anionic surfactant along with the B0503-1 to giveacceptable IFT and viscosity values.

The brine from the Field B contained 13,500 ppm total dissolved solids,620 ppm multivalent cations and the crude oil had an API Gravity of 18.The bottom hole temperature was 48° C. B0503-2 was prepared by adding 1part by weight of the sodium salt of C1416 arylalkyl xylene sulfonicacid, designated XSA-1416 and prepared as described according to U.S.Pat. No. 6,043,391, to 10 parts by weight of B0503-1. As shown in Table2, B0503-1 used alone did not provide low IFT and proper viscosity inthe oil and brine from Oil Field B. However, by adding the anionicsurfactant the IFT was lowered and the viscosity was increased. TABLE 2IFT and Viscosity Properties for Oil Field B B0503-1, 0.5% B0503-2, 0.5%IFT, mN/m 0.094 0.0085 Visc @ 12 RPM, cps 12 35 Visc @ 30 RPM, cps 8 24

EXAMPLE 3

This example illustrates the oil recovery obtained from columns packedwith crushed core from Oil Field B.

Two separate but identical columns were prepared by adding 150 grams ofthe oil saturated crushed core from Oil Field B to glass chromatographycolumns 7 inches long and 1 inch in diameter. The oil saturated crushedcore was prepared by mixing 16% by weight of the crude oil with 84% byweight of the crushed core. The columns were carefully prepared toeliminate air during packing. The Pore Volume (PV) of the columns wasdetermined to be approximately 70% or 105 ml. This is the amount ofliquid required for one displacement through the column. Each columncontained 150 g×0.16=24 g oil. Injection field brine was passed throughthe bottom of each column and collected in fractions of approximately0.5 PV (approximately 52.5 ml) each from the top. The brine was injectedinto the bottom of the columns until all the free oil was removed. Thenan additional 3.5 PV of the brine was injected prior to the addition of0.3 PV (equivalent to 31.5 ml) of a 0.5% by weight of B0503-2 in brineto column A. This was followed by injection brine. Effluents werecollected and the amount of oil recovered was measured. Only brine wasinjected into Column B as the control. The data shown in Table 3indicates that a total of more than 15.55 grams or 65% oil was recoveredfrom column A and no oil was recovered from column B. This example showsthat chemical flooding using the composition and process of the presentinvention can remove significant amount of the oil remaining afterwaterflooding. TABLE 3 Oil Recovered From Crushed Core Packed ColumnTest PV Column A Column B 0.5 0 0 1.0 0 0 1.5 0 0 2.0 0 0 2.5 0 0 3.0 00 3.5* 5 0 4.0 4 0 4.5 3 0 5.0 2 0 5.5 1 0 6.0 0.25 0 6.5 0.1 0 7.0 0.10 7.5 0.1 0 8.0 >0.1 0*begin injection of 0.3 PV of 0.5% B0503-2 in Column A only

FIG. 1 shows the detailed results obtained when 0.3 PV of a 0.5 weightpercent B0503-2 was used in column A.

EXAMPLE 4

This example illustrates the synergistic effect obtained when usingcombinations of amphoteric alkyl amido betaine surfactants, anionicsurfactants and polymers. The amphoteric alkyl amido betaine surfactantgels trend to lose their viscosity when contacting certain hydrocarbons.Additional polymer can be added to maintain the residual viscosityrequired for mobility control. This example uses oil and brine from aKansas oil field, designated as Oil Field C, contained 8,300 ppm totaldissolved solids, 80 ppm divalent cations and the crude oil had an APIGravity of 23 with a bottom hole temperature of 32° C.

A canola amidopropyl dimethyl betaine, designated B0503-3, was preparedusing the procedure as described in example 1, using canola oil as thefatty acid source. It can be seen from Table 4 that the viscosity of thebrine solution containing 0.45% B0503-3 provided an IFT of 0.092 mN/mand a viscosity of 62 cps. Linear dodecylbenzene sulfonate, designatedas LAB-1, was used as the additional anionic surfactant to enhance theIFT and viscosity properties. The data in Table 4 shows that 0.05% ofthe LAB-1 precipitated in the brine from Oil Field C due to itsintolerance to high concentrations of salt and multivalent cations.However, LAB-1 did not precipitate when added as an additional secondarysurfactant along with B0503-3. The combination of the two surfactantsperformed synergistically to provide an IFT of 0.055 mN/m and aviscosity of 81 cps. The addition of the polymer provided residualviscosity for mobility control since the viscosity provided by theB0503-3 was found to decrease dramatically when contacting the oil fromOil Field C. Without being bound by any particular theory, we believethe amphoteric alkyl amido betaine surfactant complexes with the anionicsurfactant to form a wormlike structure having high viscosity andpreventing the anionic surfactant from precipitation when contacting themultivalent cations present in the brine. When these micelles contactoil, the wormlike structure breaks up freeing the surfactant andallowing it to lower the IFT but also lowering the viscosity of theviscoelastic surfactant gel solution. Polymer is not affected by contactwith oil so when it is included it provides some residual viscosityafter the wormlike structures are broken by the oil. Thus thecombination of amphoteric alkyl amido betaine surfactant and the anionicsurfactant can increase the viscosity of the injection fluid and ispreferentially directed to oil-bearing sections of the formation wherethe surfactant is freed to lower the IFT and overcome the capillaryforces trapping the oil. The polymer then provides enough residualviscosity to mobilize the freed oil. In cases where low viscosity oil isencountered the polymer may not be necessary to provide residualviscosity. TABLE 4 Synergistic Effects Sample No. Description IFT, mN/mViscosity, cps A 0.05% LAB-1 Precipitate Precipitate B 0.45% B0503-30.092 62 C A + B before contact with 0.055 81 oil D A + B after contactwith oil 0.0042 2.7 E 0.010% Polymer 2.8 10 F Sample C + Sample E 0.09990 G Sample D + Sample E 0.0051 11

EXAMPLE 5

This example illustrates the superior viscosity characteristics of thecompositions of the present invention. The test data shows the viscosityof the viscoelastic surfactant gel is shear sensitive but reversible.Lower viscosities are expected when the amphoteric viscoelasticsurfactant gel is pumped into the reservoir at high shear and higherviscosities will be re-established when the shear is diminished withinthe reservoir.

FIG. 2 shows the viscosity versus shear rate using 0.5 per cent byweight B0503-3 in seawater. Viscosities were measured at 25° C. using aBrookfield Model LVT viscometer at various RPM. The data in FIG. 2 showsthe viscosity is very high, reaching 57 CPS, at the lower shear rate of6 RPM and is 15.1 CPS at the higher shear rate of 60 RPM. The shearthinning properties were foamed to be completely reversible.

Detailed descriptions of the preferred embodiment are provided herein.It is to be understood, however, that the present invention may beembodied in various forms. Therefore, specific details disclosed hereinare not to be interpreted as limiting, but rather as a basis for theclaims and as a representative basis for teaching one skilled in the artto employ the present invention in virtually any appropriately detailedsystem, structure or manner.

1. A composition for the recovery of oil comprising: a) one or moreamphoteric surfactants chosen for their ability to both lowerinterfacial tension and increase viscosity, b) an aqueous medium, and;c) optionally one or more polymers to provide residual viscosity.
 2. Thecomposition for the recovery of oil described in claim 1 where the oneor more amphoteric surfactants are present in amounts from about 0.1% toabout 10% by weight.
 3. The composition for the recovery of oildescribed in claim 1 where the one or more amphoteric surfactants havethe following structure:

Where, R₁ and R₂ are the same or different and preferably represent alow molecular weight alkyl residue, especially straight-chain alkylresidue with 1 to 4 carbon atoms, or hydroxy alkane; and R is C12 toC30, preferably C16 to C24 alkane or alkylene, and n is 2 to
 6. 4. Thecomposition for the recovery of oil described in claim 1 where theaqueous medium is water.
 5. The composition for the recovery of oildescribed in claim 1 where the aqueous medium is water containing saltsof mono and multivalent cations.
 6. The composition for the recovery ofoil described in claim 1 where the aqueous medium is an oilfield brine.7. The composition for the recovery of oil described in claim 1 wherethe polymer used to provide residual viscosity is a polymer chosen fromthe group: polyacrylamide, partially hydrolyzed polyacrylamide, xanthangum, guar gum, hydroxyethyl cellulose.
 8. The composition for therecovery of oil described in claim 1 where the optional polymer used toprovide residual viscosity is used at concentrations from about 0.01% toabout 0.5% by weight.
 9. A composition for the recovery of oilcomprising: a. one or more amphoteric surfactants chosen for theirability to both lower interfacial tension and increase viscosity, b. anaqueous medium, c. a secondary surfactant and; d. optionally one or morepolymers to provide residual viscosity.
 10. The composition for therecovery of oil described in claim 9 where the one or more amphotericsurfactants are present in amounts from about 0.1% to about 10% byweight.
 11. The composition for the recovery of oil described in claim 9where the one or more amphoteric surfactants have the followingstructure:

Where, R₁ and R₂ are the same or different and preferably represent alow molecular weight alkyl residue, especially straight-chain alkylresidue with 1 to 4 carbon atoms, or hydroxy alkane; and R is C12 toC30, preferably C16 to C24 alkane or alkylene, and n is 2 to
 6. 12. Thecomposition for the recovery of oil described in claim 9 where theaqueous medium is water.
 13. The composition for the recovery of oildescribed in claim 9 where the aqueous medium is water containing saltsof mono and multivalent cations.
 14. The composition for the recovery ofoil described in claim 9 where the aqueous medium is an oilfield brine.15. The composition for the recovery of oil described in claim 9 wherethe secondary surfactant is chosen from the group: anionic, nonionic,cationic surfactant.
 16. The composition for the recovery of oildescribed in claim 9 where the polymer used to provide residualviscosity is a polymer chosen from the group: polyacrylamide, partiallyhydrolyzed polyacrylamide, xanthan gum, guar gum, hydroxyethylcellulose.
 17. The composition for the recovery of oil described inclaim 9 where the polymer used to provide residual viscosity is used atconcentrations from about 0.01% to about 0.5% by weight.